In many optical applications, linearization of the optical device is an important consideration. For example, semiconductor lasers used for analog applications such as wireless transmission generally need to exhibit linearity.
Negative feedback is a standard technique for achieving linearity. In such techniques, a portion of the optical output is tapped off, converted to an electrical signal, and fed back to the drive circuit. In the normal method, the feedback cancels out a portion of the in-band signal thus producing a reduction in the gain of the system. Consequently, improvement in linearity is limited by the amount of gain reduction which is acceptable. Furthermore, difficulty is often encountered in controlling the amplitude and phase of the negative feedback loop in order to avoid unwanted oscillations of the circuit.